We report for the first time to our knowledge on noncritical temperature tuned second harmonic generation (SHG) in Li/sub 2/B/sub 4/O/sub 7/ (LB4) with the 488 nm line ofa cw Ar/sup +/ laser. LB4 is a negative uniaxial crystal belonging to the point group 4mm which means that its effective nonlinearity for type-I interaction is maximized in the noncritical (/spl theta/=90/spl deg/) limit. The spectral linewidth of 6 GHz for the 488-nm Ar/sup +/-laser line should allow in principle the use of LB4 crystals as long as 10 cm. We used for the present experiment LB4 samples of length l=1 cm and 5 cm cut at /spl theta/=90/spl deg/ with apertures of 3/spl times/5 mm and 6/spl times/10 mm, respectively. The Ar/sup +/ laser provided 10 W of maximum cw power (measured after the focusing lens and in front of the LB4 sample) in the multimode regime. After frequency doubling the radiation at the fundamental was removed using a 45/spl deg/ dielectric reflective mirror and a 60/spl deg/ fused silica prism. Absolute measurements of the second harmonic power at 244 nm were performed by a calibrated solar blind photomultiplier and a lock-in amplifier. In each case the incident power on the photomultiplier was attenuated by a 2-mm thick UG5 filter and one or two reflecting neutral density filters to levels within the linear response region of the photomultiplier.
Second harmonic generation of cw laser radiation at 244 nm by temperature tuned noncritical phase-matching in lithium tetraborate
1999-01-01
191763 byte
Conference paper
Electronic Resource
English
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